Material for producing a metallic coating on the inner surfaces of a cathode ray tube

ABSTRACT

A METAL SUPPORT CONTAINING A QUANTITY OF A METALLIC MIXTURE INCLUDING AN ALUMINUM AND MAGNESIUM ALLOY WHICH, WHEN HEATED TO THE PROPER TEMPERATURE WILL FLASH CAUSING THE MAGNESIUM TO VAPORIZE. THE MAGNESIUM VAPOR WILL CONDENSE ON THE INSIDE SURFACES OF THE TUBE. THE MIXTURE ALSO CONTAINS A METAL IN THE FREE STATE WHICH WILL COMBINE WITH THE ALUMINUM DURING AND SUBSEQUENT TO THE VAPORIZATION OF THE MAGNESIUM PREVENTING THE FORMATION OF LOOSE PARTICLES OF ALUMINUM, AND ALSO PREVENTING MOLTEN ALUMINUM FROM ATTACKING THE SUPPORT.

MATERIAL FOR PRODUCING A METALLIC COAT- v ING ON THE INNER SURFACES OF A CA'I HODE RAY TUBE Frederick P. Scott, Syracuse, N.Y., assignor to King Laboratories, Inc., Syracuse, NY. No Drawing. Filed May 8, 1972, Ser. No. 251,029 Int. Cl. B22t' 1/00 US. Cl. 75-.5 R 8 Claims ABSTRACT OF THE DISCLOSURE A metal support containing a quantity of a metallic mixture including an aluminum and magnesium alloy which, when heated to the proper temperature will fiash causing the magnesium to vaporize. The magnesium vapor will condense on the inside surfaces of the tube. The mixture also contains a metal in the free state which will combine with the aluminum during and subsequent to the vaporization of the magnesium preventing the formation of loose particles of aluminum, and also preventing molten aluminum from attacking the support.

BACKGROUND OF 'I HE INVENTION It is known that a conductive coating on the inside of the envelope of a cathode ray tube produces a field free space within the tube permitting the electron beam to reach the screen without distortion. This is accomplished by maintaining an anodic potential on the coating by virtue of an electrical connection extending through the glass envelope of the tube.

At present, the conventional practice to produce the conductive coating is by applying, either manually or by spraying techniques, what is essentially a suspension of graphite and water to the inner surface of the tube envelope.

While the graphite coating, properly applied, operates satisfactorily in a tube that has been correctly made, it does introduce technical and production difiiculties which must be overcome by the expenditure of manual labor and the use of extensive equipment. -It is also well known that the cathode ray tubes operate under high vacuum conditions. Accordingly, it becomes most important to remove or reduce to a negligible amount any potentially contaminated gases that may be introduced in the tube during the manufacture thereof.

Coating the inside Walls of the tube with a water graphite slurry introduced a very large quantity of water which must be removed by extensive baking at high temperatures and while the tube is being evacuated. .Also, the graphite coating, because of the nature of its composition, has a tendency for producing loose, solid particles which can be detrimental to the finished tube.

SUMMARY OF THE INVENTION .A quantity of a metallic mixture is contained in a metal support adapted to be placed in the tube. The mixture includes an alloy containing aluminum and a metal having a high vapor pressure preferably magnesium. The mixture also includes a free metal stable under normal conditions and which, when the alloy is heated to a temperature to vaporize the magnesium, will combine with the aluminum to prevent the presence of free particles of aluminum. The support and the alloy are heated subsequent to the evacuation of the tube in a manner similar to the flashing of a getter.

The invention has as an object a device for use in producing an electrical conductive coating on the inside surface of a cathode ray tube without introducing any undesirable gases or other material.

3,826,645 Patented July 30, 1974 DESCRIPTION OF THE PREFERRED EMBODIMENT vacuum tubes and conventionally referred to as getters.

The material is a mixture containing an alloy of aluminum and magnesium, and also a reducing metal in free state. The support is positioned within the tube and after the same has been evacuated, the support and the alloy are heated to a temperature at which the magnesium will vaporize. The heating of the support and the alloy contained therein is after the fashion of flashing a getter.

Due to the high vapor pressure of the magnesium it will begin to vaporize at a temperature below the melting point of the aluminum. However, the application of heat is continued, as conventionally in the case of flashing a getter in order to obtain the maximum yield, in this case of magnesium vapor. Accordingly, the temperature of the alloy in the mixture is raised to a level at which the magnesium will evaporate. This action will result in the aluminum being set free with the possibility that particles of aluminum may be formed. To. avoid that undesirable situation I include in the mixture a metal of the type, which, from a practical standpoint, is stable under normal conditions, and which has the characteristics of combining With the aluminum to prevent the production of free particles of aluminum.

Normally, the support includes ferrous metal. The support may be made of iron or stainless steel, and as is well known the molten aluminum will attack the support formed of such metal with the possibility of partially disintegrating the same. The inclusion of the combining metal will also avoid that problem.

To avoid such problems, I include in the mixture a metal selected from the group consisting of iron, nickel, cobalt, titanium, zirconium or rare earths or misch metal. These metals are stable under normal and ordinary conditions, each having a heat of vaporization considerably above that of the magnesium.

The mixture may be produced by grinding an alloy of aluminum and magnesium and adding thereto one of the metals abovementioned in powdered form.

As previously stated, when the support and mixture are heated to the temperature to elfect vaporization of the magnesium, the reducing metal combines with the aluminum, and the same becomes fixed to the support and thereby prevents the formation of loose par-ticles. As previously stated, the vapor pressure of the magnesium is substantially above that of the reducing metal and accordingly the magnesium is flashed from the mixture at a temperature below vaporization of the reducing metal.

The prepared alloy contains from 30 to aluminum and 30 to 70% magnesium. T 0 make up the final mixture there is added 30 to 70% of the reducing metal. The above percentages are by weight. A particularly satisfactory mixture is one containing an alloy of 40% aluminum and 60% magnesium. To that is added an amount of nickel equal to the weight of the alloy. In other words, that mixture contains 20% aluminum, 30% magnesium, and 50% nickel.

It will be understood that the quantities of metal constituting the alloy will be determined on the amount of magnesium necessary to provide a satisfactory coating on the inner surface of a given cathode ray tube.

I claim:

1. A vapor deposition material for use in producing a conductive coating on the interior surface of evacuated and sealed cathode ray tubes, vacuum tube and the like .lbty exposure. to..radiant energy, including -.an. alloy con-..

a when heated being capable of combining with the aluminum in the alloy to raise the temperature of the mixture sufficient to vaporize the magnesium.

2. The material of claim 1 whereinthe reducing metal is a member of'the group comprising iron, nickel, cobalt, titanium, zirconium and rare earths.

3. The material of claim 1 wherein the reducing metal consists of free nickel.

4. The material of claim 1 wherein the reducing metal consists of free cobalt.

5. The material of claim 1 wherein the reducing metal consists of free titanium.

6. The material of claim 1 wherein the reducing metal consists of free zirconium.

Ihezmaterialwof; claim 1 wherein the reducing metal consists of rare earths.

8. The material of claim 1 wherein the reducing metal consists of free iron. 1

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- UNITED STATES PATENTS. v

Salveter, Jr 1-l7-97 3,582,394 6/1971 3,246,626 4/1966 "Betar' 1l8-49 3,443,138 5/1969 Schwartz 313' 64 3,486,001 12/1969 Cz'arnowski .1 18 -48 

